Kochi: The Kerala University of Fisheries and Ocean Studies (KUFOS) has found highly toxic levels of sulfide and ammonia in the samples of water collected from the Periyar a day after the river witnessed a massive fish kill.

The report came a day after the State Pollution Control Board cited depletion of dissolved oxygen as the cause of the massive fish death. The KUFOS report also found lower levels of dissolved oxygen in the water.

The PCB report states that it could not find any trace of industrial effluents in the water samples, in stark contrast to the local fish farmers’ allegation that the uncontrolled discharge of pollutants by industrial units along the Periyar caused the fish death.

The fisheries’ varsity tested the water samples it collected from the river on Tuesday (May 21) while the PCB report mentions that the samples were taken on Monday night (May 20) soon after the fish kill was reported.

“Our preliminary study has found highly toxic levels of sulfide and ammonia in the water we tested. The results turned out similar for samples taken from different spots. The substances might have git into the water from rotten fish too. It would take at least two weeks to complete the tests on the samples of dead fish,” a KUFOS source told Onmanorama.

The PCB has tested the samples taken from various spots in the river and its report has blamed the irrigation department for causing the depletion of dissolved oxygen in the water with the sudden opening of the shutter of Pathalam regulator-cum-bridge.

"After the rain intensified, three shutters of Pathalam regulator-cum-bridge were opened on Monday evening. Then water with a low amount of dissolved oxygen flowed down the regulator in large quantity leading to the fish kill. It has been noticed that organic waste accumulates on the top of the regulator when the bund remains shut during summer. The sudden and continuous outflow of the water when the bund opened caused the depletion of dissolved oxygen downstream. The Irrigation department has been given a directive since 2018 to maintain lean flow in the river. A direction was issued also on January 10. The irrigation department did not take steps to sustain lean flow or inform the board about opening the shutters,” the PCB report said.

The PCB said five industrial units have been permitted to discharge treated effluents to the Periyar. The report said untreated or illegal discharge of effluents could not be found.

However, it issued a closure memo to Alliance Marine, a factory treating chicken waste on May 22.

The fish kill was reported from Monday night in places such as Vettukadav, Eloor Ferry, Cheranalloor, Varapuzha, Kadamakudy and Kothad. The fisheries department has assessed losses to the tune of Rs 10 crore for the inland fish farmers in the region.